Communication Units, Integrated Circuits and Methods for Supporting a Virtual Carrier

ABSTRACT

A network element for controlling a usage of at least one resource is described. The network element comprises: a transmitter for transmitting a signal identifying at least one uplink resource to at least one wireless communication unit; a signal processor operably coupled to the transmitter for generating the signal; and a receiver for receiving a transmission from the at least one wireless communication unit on the identified at least one uplink resource. The signal processor is arranged to allocate the uplink resource for the at least one wireless communication unit in a first portion of a first sub-frame on a first frequency and a first portion of a second sub-frame on a second frequency wherein a time gap is allocated between an end of the first portion of the first sub-frame and a beginning of the first portion of a second sub-frame.

RELATED APPLICATION(S)

This is a continuation of U.S. patent application Ser. No. 13/719,812,Filed Dec. 19, 2012, entitled COMMUNICATION UNITS, INTEGRATED CIRCUITSAND METHODS FOR SUPPORTING A VIRTUAL CARRIER, which application claimsthe benefit of United Kingdom Application No. 1214137.0 filed Aug. 7,2012. The content of these applications are fully incorporated herein intheir entirety.

FIELD OF THE INVENTION

The field of this invention relates to communication units, integratedcircuits and methods for scheduling resource, and in particular forsupporting physical uplink control channel signals in a low bandwidthdevice.

BACKGROUND OF THE INVENTION

A recent development of third generation (3G) wireless communications isthe long term evolution (LTE) cellular communication standard, sometimesreferred to as a 4^(th) generation (4G) system. 4G systems will bedeployed in existing spectral allocations owned by network operators andnew spectral allocations that are yet to be licensed.

LTE devices are able to operate on carriers of bandwidth up to 20 MHz.The requirement to support a bandwidth of up to 20 MHz increases devicecost in comparison to lower bandwidth systems, such as the GeneralPacket Radio Service (GPRS). The cost of supporting high bandwidthdevices has led to an increasing desire to support additional lowbandwidth (and hence low cost) LTE devices within higher bandwidthcarriers. In particular, UEs and corresponding base stations (oftenreferred to as evolved NodeBs (eNodeBs) in 3GPP parlance) have beendeveloped that utilise low bandwidth carriers operating within thebandwidth of a higher bandwidth host carrier.

Examples of devices that could beneficially use low bandwidth carriersinclude devices used for so-called machine type communication (MTC)applications, which are typified by semi-autonomous or autonomouswireless communication devices (i.e. MTC devices) communicating smallamounts of data on a relatively infrequent basis. Examples of MTCdevices include so-called smart meters, which, for example, may belocated in a customer's house and periodically transmit information backto a central MTC server data relating to the customer's consumption of autility such as gas, water, electricity and so on.

Whilst it can be convenient for a terminal such as an MTC type terminalto take advantage of the wide coverage area provided by a third orfourth generation mobile telecommunication network, there are at presentdisadvantages. Unlike a conventional third or fourth generation mobileterminal such as a smartphone, an MTC-type terminal is preferablyrelatively simple and inexpensive. The type of functions performed bythe MTC-type terminal (e.g. collecting and reporting back data to thenetwork) do not require particularly complex processing to be performed.In many scenarios, providing low capability terminals with aconventional high-performance LTE receiver unit capable of receiving andprocessing data from an LTE downlink frame across the full carrierbandwidth can be overly complex and expensive for a device that onlyneeds to communicate small amounts of data.

There has been a particular interest in utilising LTE for machine typecommunications, as it is more spectrally efficient than the GPRS serviceand would allow network operators to reduce their operating costs.However a device utilising LTE is not as cost effective as a deviceutilising the 2.5G service (GPRS) due to the LTE requirement for the MTCterminal to operate in a high bandwidth carrier.

MTC application solution providers will be motivated to use LTE devices,which is in the interest of network operators, if the cost of LTEdevices is reduced such that they are comparable in cost terms to GPRSdevices. There are numerous ways of reducing the cost of LTE devices;however one of the most promising, and potentially most effective,techniques is reducing the supported bandwidth that a device can operatein. The LTE standard is currently considering use of ‘virtual carriers’in order to support low bandwidth UEs, whilst concurrently maintainingthe current host carrier architecture, within which the virtual carrieroperates.

Virtual carriers occupy a restricted set of symbols within thesub-frame. Specifically, virtual carriers do not occupy the symbols thatare used by the host carrier to transmit the host carrier's controlchannels, e.g. physical downlink control channel (PDCCH), physicalhybrid automatic repeat request (ARQ) indicator channel (PHICH) andphysical control format indicator channel (PCFICH). Instead, virtualcarriers contain narrow bandwidth VC-PDCCH, VC-PHICH and VC-PCFICHcontrol channels, where these virtual carrier control channels occupysymbols other than those occupied by the host carrier. Virtual carriersdo not need to contain their own synchronization signals and UEs may usethe synchronization signals transmitted by the host carrier forsynchronization purposes. Additionally, virtual carriers do not need tocontain a physical broadcast channel (PBCH) and UEs again may rely onthe PBCH transmitted in the host carrier for the signalling of someelements of system information within a master information block. Thesystem information for the virtual carrier may be shared with the systeminformation for the host carrier.

In addition to the above opportunities and constraints, the use ofvirtual carriers may allow low bandwidth UEs to co-exist on the samecarrier with legacy UEs. A legacy UE would generally need to decodecontrol channel information across the entire channel bandwidth. Asillustrated in FIG. 1, the LTE channel bandwidth can be up to 20 MHz,though other channel bandwidths such as 15 MHz, 10 MHz, 5 MHz, 3 MHz and1.4 MHz are also supported. However, as mentioned, a low bandwidth UEwould not be able to decode all the information from the entire channelbandwidth in the host carrier when a virtual carrier is used, as the lowbandwidth UE will only have the capability to operate in a relativelynarrow bandwidth, due to cost considerations associated with thehardware required to operate in a wider bandwidth.

FIG. 1 illustrates a schematic diagram of a sub-frame of a known hostlegacy carrier 100 comprising a legacy control channel region 110,legacy physical broadcast channel (PBCH) 145 and synchronization signals105, legacy data region 135, virtual carrier 130, virtual carrier dataregions 120, 125 and virtual carrier control channel region 115. FIG. 1also shows the first sub-frame of a 10 msec. radio frame. The sixthsub-frame of the radio frame does not contain the PBCH; the other eightsub-frames of the radio frame contain neither synchronization signalsnor the PBCH. Since the control channels of the host carrier occupy theentire system bandwidth, it is desirable to have a separate lowbandwidth control channel region for low bandwidth UEs in order toenable both types of UE to operate on the same carrier.

As legacy UEs decode their control channels across the entire carrierbandwidth, they may therefore be scheduled physical downlink sharedchannel (PDSCH) resource in subcarriers outside the bandwidth of thevirtual carrier 130. In this manner the virtual carrier is effectivelytransparent to the legacy UEs that are scheduled in the host carrier.

It is possible to have multiple virtual carriers supported by a hostlegacy carrier. However, the virtual carriers can only exist in physicalresources that are not occupied by the host carrier's control channels.From the viewpoint of legacy UEs that are not allocated resources in thevirtual carrier, the host carrier, with the incorporated virtualcarrier, is identical to the structure of a host carrier in Release 8-103GPP™ networks.

In current 3GPP™ releases (up to Release-10), the physical uplinkcontrol channel (PUCCH) is transmitted in a frequency distributedmanner. Specifically, the PUCCH is transmitted in different subcarriersin each timeslot of the same sub-frame. Since a legacy UE's RF circuitsare able to transmit across the same bandwidth that the eNodeB operatesin, switching the sub-carriers that the UE uses to transmit the PUCCH(at timeslot boundaries within the sub-frame) is not an onerous task.

FIG. 1 further illustrates a schematic diagram 140 of PUCCH operationfor UEs of existing Releases, e.g. Release 8-10 UEs. The schematicdiagram 140 comprises a host carrier bandwidth 148 that supports atleast a first sub-frame 156 comprising two timeslots ‘A’, ‘B’ 142carrying a PUCCH signal 154 for a first UE, where the PUCCH signal 154for a first UE is sent in a low frequency 150 in timeslot ‘A’ and sentin a high frequency 152 in timeslot ‘B’ and the PUCCH signal 144 for asecond UE is sent in a high frequency 151 in timeslot ‘A’ and sent in alow frequency 153 in timeslot ‘B’.

However for low bandwidth UEs, a problem arises as the low bandwidth UEis unable to receive in the manner shown in 140 as the low bandwidth UEis unable to receive signals or re-tune its synthesisers and otherfrequency-sensitive components of its RF circuits across the fullbandwidth 148 from low frequency 150 to high frequency 152 from timeslot‘A’ to timeslot ‘B’. A legacy UE does not have this problem because itsRF circuits operate across the entire carrier bandwidth 148.

One solution to the above problem that is known in the prior art is theuse of an uplink virtual carrier. FIG. 1 further illustrates a schematicdiagram of such an uplink virtual carrier operation of PUCCH 160comprising PUCCH resources to be used by legacy UEs 174 and PUCCHresources to be used by a low bandwidth UE 176. The schematic diagramshows a virtual carrier that uses low frequency subcarriers 164 for somefirst PUCCHs in a first timeslot 162 of a sub-frame 178 and higherfrequency subcarriers 166 for other second PUCCHs in a second timeslot,where the difference in frequencies between the low frequencysubcarriers 164 and the higher frequency subcarriers 166 is less thanthe difference in frequency of the subcarriers used by the PUCCHresources for the legacy UEs 174; in the second timeslot of thesub-frame 178, the first PUCCHs use the higher frequency subcarriers andthe second PUCCHs use the lower frequency subcarriers. As illustrated,the bandwidth, across which the PUCCH operates for the virtual carrier,is constrained between the subcarriers 164 and the subcarriers 166; andthis bandwidth is less than the bandwidth 172 occupied by the hostcarrier. This reduced bandwidth of operation allows a low bandwidth UEto operate in the uplink, albeit in a narrower bandwidth than a legacyUE.

However, a problem with the proposed solution illustrated in 160 is thatthe bandwidth of the host carrier 174 has been fragmented, and is nolonger contiguous. Therefore, first carrier region 170 and secondcarrier region 168 can only be applied to separate legacy UEs, andcannot be utilised by a single legacy UE.

Therefore, there is a desire to better support scheduling of resourcesto both legacy and low bandwidth UEs, for example with physical uplinkcontrol channel signals, for example without fragmenting the hostcarrier bandwidth.

SUMMARY OF THE INVENTION

The present invention provides communications units, integrated circuitsand methods of scheduling of resources, for example for operating on avirtual carrier, as described in the accompanying claims. Specificembodiments of the invention are set forth in the dependent claims.These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematic examples of a known host carrier andvirtual carrier arrangement.

FIG. 2 illustrates a 3GPP™ LTE cellular communication system adapted inaccordance with some example embodiments of the present invention.

FIG. 3 illustrates a wireless communication unit adapted in accordancewith some example embodiments of the present invention.

FIG. 4 illustrates a schematic diagram of an example of a conventionalLTE downlink radio sub-frame.

FIG. 5 illustrates a schematic diagram of the first sub-frame of an LTEdownlink radio sub-frame in which a virtual carrier has been inserted.

FIG. 6 illustrates a schematic diagram of an example of an adapted LTE‘camp-on’ procedure for camping on to a virtual carrier.

FIG. 7 illustrates PUCCH operation for a low bandwidth UE according toan example embodiment of the invention.

FIG. 8 illustrates a flowchart of a UE operation according to an exampleembodiment of the invention.

FIG. 9 illustrates a schematic diagram of ‘grouped’ scheduling of PUCCHsaccording to an example embodiment of the invention.

FIG. 10 illustrates a schematic of semi-statically assigned PUCCHresources for ‘grouped’ UEs according to an example embodiment of theinvention.

FIG. 11 illustrates a flow chart of eNodeB operation for ‘grouped’ UEsaccording to an example embodiment of the invention.

FIG. 12 illustrates a further schematic diagram of ‘grouped’ schedulingof PUCCHs according to an example embodiment of the invention.

FIG. 13 illustrates a schematic diagram of mapping between PDCCH andPUCCH according to an example embodiment of the invention.

FIG. 14 illustrates a flow chart of eNodeB scheduling of PDSCH to UEsaccording to an example embodiment of the invention.

DETAILED DESCRIPTION

Referring now to FIG. 2, a wireless communication system 200 is shown inoutline, in accordance with one example embodiment of the invention. Inthis example embodiment, the wireless communication system 200 iscompliant with, and contains network elements capable of operating over,a universal mobile telecommunication system (UMTS™) air-interface. Inparticular, the embodiment relates to a system's architecture for anEvolved-UMTS Terrestrial Radio Access Network (E-UTRAN) wirelesscommunication system, which is currently under discussion in the thirdGeneration Partnership Project (3GPP™) specification for long termevolution (LTE), based around OFDMA (Orthogonal Frequency DivisionMultiple Access) in the downlink (DL) and SC-FDMA (Single CarrierFrequency Division Multiple Access) in the uplink (UL), as described inthe 3GPP™ TS 36.xxx series of specifications. Within LTE, both timedivision duplex (TDD) and frequency division duplex (FDD) modes aredefined.

The wireless communication system 200 architecture consists of radioaccess network (RAN) and core network (CN) elements 204, with the corenetwork elements 204 being coupled to external networks 202 (namedPacket Data Networks (PDNs)), such as the Internet or a corporatenetwork. The CN elements 204 comprise a network element 207, which in apacket data network supporting general packet data traffic may be apacket data network gateway (P-GW), and in a Multimedia Broadcast andMulticast Service (MBMS) network providing MBMS service may be aBroadcast/Multicast Service Center (BM-SC). In order to serve up localcontent, the P-GW may be coupled to a content provider. The P-GW 207 maybe further coupled to a policy control and rules function entity (PCRF)297 and a Gateway 206.

The PCRF 297 is operable to control policy control decision making, aswell as for controlling the flow-based charging functionalities in apolicy control enforcement function PCEF (not shown) that may reside inthe P-GW 207. The PCRF 297 may further provide a quality of service(QoS) authorisation class identifier and bit rate information thatdictates how a certain data flow will be treated in the PCEF, andensures that this is in accordance with a UE's 225 subscription profile.

In example embodiments, the Gateway 206 may be an MBMS or a ServingGateway (S-GW). The Gateway 206 is coupled to a mobility managemententity MME 208 via an S11 interface. The MME 208 is operable to managesession control of Gateway bearers and is operably coupled to a homesubscriber server (HSS) database 230 that is arranged to storesubscriber communication unit 225 (user equipment (UE)) relatedinformation.

The HSS database 230 may store UE subscription data, such as QoSprofiles and any access restrictions for roaming. The HSS database 230may also store information relating to the P-GW 207 to which a UE 225can connect. For example, this data may be in the form of an accesspoint name (APN) or a packet data network (PDN) address. In addition,the HSS database 230 may hold dynamic information relating to theidentity of the MME 208 to which a UE 225 is currently connected orregistered.

The MME 208 may be further operable to control protocols running betweenthe user equipment (UE) 225 and the CN elements 204, which are commonlyknown as Non-Access Stratum (NAS) protocols. The MME 208 may support atleast the following functions that can be classified as: functionsrelating to bearer management (which may include the establishment,maintenance and release of bearers), functions relating to connectionmanagement (which may include the establishment of the connection andsecurity between the network and the UE 225) and functions relating tointer-working with other networks (which may include the handover ofvoice calls to legacy networks). The Gateway 206 predominantly acts as amobility anchor point and is capable of providing internet protocol (IP)multicast distribution of user plane data to eNodeBs 210. The Gateway206 may receive content via the P-GW 207, from one or more contentproviders 209 or via the external PDN 202. The MME 208 may be furthercoupled to an evolved serving mobile location centre (E-SMLC) 298 and agateway mobile location centre (GMLC) 299.

The E-SMLC 298 is operable to manage the overall coordination andscheduling of resources required to find the location of the UE that isattached to the RAN, in this example embodiment the E-UTRAN. The GMLC299 contains functionalities required to support location services(LCS). After performing an authorisation, it sends positioning requeststo the MME 208 and receives final location estimates.

The P-GW 207 is operable to determine IP address allocation for a UE225, as well as QoS enforcement and flow-based charging according torules received from the PCRF 297. The P-GW 207 is further operable tocontrol the filtering of downlink user IP packets into differentQoS-based bearers (not shown). The P-GW 207 may also serve as a mobilityanchor for inter-working with non-3GPP technologies such as CDMA2000 andWiMAX networks.

The Gateway 206, as discussed above, may comprise an MBMS gateway or anS-GW. If Gateway 206 comprises an MBMS gateway, an MBMS co-ordinationentity (MCE) 205 may be required that would reside in the E-UTRANbetween the MME 208 and the eNodeBs 210. The MCE 205 manages the layer-2configurations and the use of the radio resources for broadcasttransmission. Thus, the MCE 205 is a radio access network (RAN) domainelement and can be either a separate entity (as shown) or located at theeNodeB 210. For user plane (UP) data, the BM-SC 207 is directly coupledto the eNodeBs 210 via an M1 interface.

If the Gateway 206 comprises an S-GW, the MCE 205 may not be required,and the eNodeBs 210 would be connected to the S-GW 206 and the MME 208directly. In this case, all UE packets would be transferred through theS-GW 206, which may serve as a local mobility anchor for the databearers when a UE 225 moves between eNodeBs 210. The S-GW 206 is alsocapable of retaining information about the bearers when the UE 225 is inan idle state (known as EPS connection management IDLE), and temporarilybuffers downlink data while the MME 208 initiates paging of the UE 225to re-establish the bearers. In addition, the S-GW 206 may perform someadministrative functions in the visited network, such as collectinginformation for charging (i.e. the volume of data sent or received fromthe UE 225). The S-GW 206 may further serve as a mobility anchor forinter-working with other 3GPP™ technologies such as GPRS™ and UMTS™.

As illustrated, the CN 204 is operably connected to two eNodeBs 210,with their respective coverage zones or cells 285, 290 and a pluralityof UEs 225 receiving transmissions from the CN 204 via the eNodeBs 210.In accordance with example embodiments of the present invention, atleast one eNodeB 210 and at least one UE 225 (amongst other elements)have been adapted to support the concepts hereinafter described.

The main component of the RAN is an eNodeB (an evolved NodeB) 210, whichperforms many standard base station functions and is connected to the CN204 via an S1 interface and to the UEs 225 via a Uu interface. Awireless communication system will typically have a large number of suchinfrastructure elements where, for clarity purposes, only a limitednumber are shown in FIG. 2. The eNodeBs 210 control and manage the radioresource related functions for a plurality of wireless subscribercommunication units/terminals (or user equipment (UE) 225 in UMTS™nomenclature). Each of the UEs 225 comprise a transceiver unit 227operably coupled to signal processing logic 308 (with one UE illustratedin such detail for clarity purposes only). The system comprises manyother UEs 225 and eNodeBs 210, which for clarity purposes are not shown.

As illustrated, each eNodeB 210 comprises one or more wirelesstransceiver unit(s) 294 that is/are operably coupled to a controlprocessor 296 and memory 292 for storing, inter alia, informationrelating to UEs and UE capabilities, for example whether the UE iscapable of operating as a low bandwidth UE.

In example embodiments of the invention, the network element, such aseNodeB 210, comprises functionality for controlling a usage of at leastone resource. In one example, the one or more wireless transceiverunit(s) 294 of the eNodeB 210 comprise(s) a transmitter for transmittinga signal identifying at least one uplink resource to at least onewireless communication unit and a receiver for receiving a transmissionfrom the at least one wireless communication unit on the identified atleast one uplink resource. The uplink PUCCH resource is often notassigned explicitly to the at least one wireless communication unit,although in some examples it may be for example where the wirelesscommunication unit is set up to transmit periodic CQI reports in LTE.Instead, the physical resources that were used by the PDCCH are oftenconfigured to map to the physical resources to be used for the PUCCH(for example if PDCCH used resource block ‘X’, the PUCCH may beconfigured to use physical resources ‘Y’, etc.).

The control processor 296 in the network element is operably coupled tothe transmitter for generating the signal. In examples of the invention,the control processor 296 is arranged to allocate the uplink resourcefor the at least one wireless communication unit in a first portion of afirst sub-frame on a first frequency and a first portion of a secondsub-frame on a second frequency wherein a time gap is allocated betweenan end of the first portion of the first sub-frame and a beginning ofthe first portion of a second sub-frame, as described hereinafter withregard to later figures.

In some examples, the time gap between the first portion of the firstsub-frame and the first portion of the second sub-frame may be arrangedby the control processor 296 to be sufficient to enable the at least onewireless communication unit 225 to switch operation from the firstfrequency to the second frequency.

In some examples, the control processor 296 may generate a first signalallocating a first uplink resource for transmission to a first wirelesscommunication unit 225 and generate a second signal allocating a seconduplink resource for transmission to a second wireless communicationunit.

In some examples, the control processor 296 may be further arranged togroup a plurality of wireless communication units by assigning a type tothe wireless communication unit, for example based at least partly onone of the following: where the relationship between resources for afirst type and a second type are known a priori; where the signalprocessor is further arranged to define a relationship between theplurality of wireless communication units for use of at least one uplinkcontrol channel (PUCCH).

In some examples, UEs may be defined as being of type A or of type B andthe term ‘relationship’ may encompass how the PDSCH resources for type BUEs are related to the PDSCH resources for type A UEs. In some examples,the term ‘relationship’ may encompass how the PUCCH resources for type BUEs are related either to the PUCCH resources for type A UEs or to thePDCCH.

In some examples, the at least one uplink resource may comprise anphysical uplink control channel (PUCCH) wherein the PUCCH occupies afirst timeslot, say timeslot ‘X’, of a first sub-frame and a secondtimeslot, say timeslot ‘Y’, of a second sub-frame, where in someexamples the first timeslot and second timeslot are separated by atimeslot. Thus, in this manner, the PUCCH may be multiplexed into twotimeslots, where the timeslots are separated by a time gap (such as atimeslot). In some examples, the timeslots may be in differentsub-frames.

In some examples, the control processor 296 may allocate a set ofsubcarriers and/or timeslots in a first PUCCH resource to multiplewireless communication units, such that a plurality of wirelesscommunication units 225 may be allocated the same relative timeslot foreach subsequent sub-frame from a first set of subcarriers. In thoseresources, multiple UEs may be allocated PUCCH by virtue of those UEsbeing either frequency multiplexed (onto different subcarriers) or codemultiplexed using orthogonal spreading codes.

In some examples, the control processor 296 may be further arranged togroup the plurality of wireless communication units according to thewireless communication unit type based at least partly on one of thefollowing: where the relationship between resources for a first type anda second type are known a priori; where the signal processor is furtherarranged to define a relationship between the plurality of wirelesscommunication units and at least one downlink control channel (PDCCH).

In some examples, the control processor 296 may be further arranged todetermine whether or not downlink data exists for the at least onewireless communication unit. A scheduler (not shown), which in someexamples may be part of or coupled to the control processor 296, mayallocate the PUCCH resource for the at least one wireless communicationunit 225 based at least partly on determining that data exists for theat least one wireless communication unit 225. In some examples, the atleast one wireless communication unit 225 (for example a UE) knows whichPUCCH to use by an implicit link between the PDCCH and PUCCH (forexample the scheduler may select which PUCCH to schedule and then workout which PDCCH it has to use in order to implicitly schedule thatPUCCH).

Referring now to FIG. 3, a block diagram of a wireless communicationunit, adapted in accordance with some example embodiments of theinvention, is shown. In practice, purely for the purposes of explainingembodiments of the invention, the wireless communication unit isdescribed in terms of a wireless subscriber communication unit, such asa UE 225. The wireless communication unit 225 contains an antenna 302coupled to an antenna switch or duplexer 304 that provides isolationbetween receive and transmit chains within the wireless communicationunit 225. One or more receiver chains, as known in the art, includereceiver front-end circuitry 306 (effectively providing reception,filtering and intermediate or base-band frequency conversion). Thereceiver front-end circuitry 306 is coupled to a signal processingmodule 308 (generally realized by a digital signal processor (DSP)). Askilled artisan will appreciate that the level of integration ofreceiver circuits or components may be, in some instances,implementation-dependent.

The controller 314 maintains overall operational control of the wirelesscommunication unit 225. The controller 314 is also coupled to thereceiver front-end circuitry 306 and the signal processing module 308.In some examples, the controller 314 is also coupled to a buffer module317 and a memory device 316 that selectively stores operating regimes,such as decoding/encoding functions, synchronization patterns, codesequences, and the like. A timer 318 is operably coupled to thecontroller 314 to control the timing of operations (e.g. transmission orreception of time-dependent signals) within the wireless communicationunit 225.

As regards the transmit chain, this essentially includes an input module320, coupled in series through transmitter/modulation circuitry 322 anda power amplifier 324 to the antenna 302, antenna array, or plurality ofantennas. The transmitter/modulation circuitry 322 and the poweramplifier 324 are operationally responsive to the controller 314.

The signal processor module 308 in the transmit chain may be implementedas distinct from the signal processor in the receive chain.Alternatively, a single processor may be used to implement a processingof both transmit and receive signals, as shown in FIG. 3. Clearly, thevarious components within the wireless communication unit 225 can berealized in discrete or integrated component form, with an ultimatestructure therefore being an application-specific or design selection.

Referring now to FIG. 4 a schematic diagram illustrating an OFDM basedLTE downlink radio frame 400 is illustrated. The LTE downlink radioframe is transmitted from an LTE base station (known as an enhanced NodeB) and is of 10 msec. in length. The downlink radio frame 420 comprisesten sub-frames, each sub-frame being of 1 msec. in length. A firstinstance of the primary synchronization signal (PSS) and a secondarysynchronization signal (SSS) is transmitted in the first 405 sub-frameof the LTE frame and a second instance of the PSS and SSS is transmittedin the sixth 425 sub-frame of the LTE frame. A physical broadcastchannel (PBCH) 410 is also transmitted in the first sub-frame of the LTEframe.

FIG. 5 shows a schematic diagram illustrating an LTE downlink sub-framethat includes a virtual carrier inserted in a host carrier in accordancewith example embodiments of the invention. In keeping with aconventional LTE downlink sub-frame, the first ‘n’ symbols (where ‘n’ isthree in FIG. 5) form the control region 500, which is reserved for thetransmission of downlink control data such as data transmitted on thePDCCH. However, as can be seen from FIG. 5, outside of the controlregion 500 the LTE downlink sub-frame includes a group of resourceelements below the central band 510 that is allocated to function as avirtual carrier 530. As will become clear, the virtual carrier 530 isadapted such that data transmitted on the virtual carrier 530 can betreated as logically distinct from the data transmitted in the remainingparts of the host carrier, and can thus and advantageously be decodedwithout first decoding all the control data from the control region 500.Although FIG. 5 shows the virtual carrier 530 occupying frequencyresources below the centre band, in other examples the virtual carrier530 may be arranged to either occupy frequency resources above thecentre band or frequency resources, including the centre band. If thevirtual carrier 530 is configured to overlap any resources used by thePSS, SSS or PBCH of the host carrier, or any other signal transmitted bythe host carrier that a mobile terminal operating on the host carrierwould require for correct operation and expect to find in a knownpre-determined location, the signals on the virtual carrier 530 can bearranged such that these aspects of the host carrier signal aremaintained. The virtual carrier 530 is shown in FIG. 5 to comprise botha virtual carrier control data region 520 and a virtual carrier dataregion 540. The virtual carrier control data region 520 may be used totransmit control channels within the virtual carrier, such as a virtualcarrier physical downlink control channel (VC-PDCCH) etc. The virtualcarrier data region 540 may be used to transmit data-bearing channels,such as a virtual carrier physical downlink shared channel (VC-PDSCH).

As illustrated in FIG. 5, data transmitted on the virtual carrier 530 istransmitted across a limited bandwidth. In some examples, the virtualcarrier may be arranged to encompass any suitable bandwidth, which inmost examples is arranged to be smaller than that of the host carrier.In the example shown in FIG. 5 the virtual carrier 530 is transmittedacross a bandwidth comprising 12 blocks of 12 sub-carriers (i.e. 144sub-carriers), which is equivalent to a 2.16 MHz transmission bandwidth.Accordingly, a terminal receiving data transmitted on the virtualcarrier need only be equipped with a receiver that is capable ofreceiving and processing data transmitted over a bandwidth of 2.16 MHz.This enables low capability terminals (for example MTC type terminals)to be provided with simplified receiver units and yet still be able tooperate within an OFDM type communication network, which, as explainedpreviously, conventionally requires terminals to be equipped withreceivers capable of receiving and processing an OFDM signal across theentire bandwidth of the signal. In other examples, the virtual carriermay occupy 6 blocks of 12 subcarriers, leading to a virtual carrieroperating in 72 subcarriers, which is equivalent to operation in a 1.08MHz transmission bandwidth.

As can be seen in FIG. 5, the final symbols of the virtual carrier 530can be reserved as a virtual carrier control region 520, which isallocated for the transmission of hybrid ARQ acknowledgements via aVC-PHICH, PDSCH allocations via a VC-PDCCH, the number of symbolsoccupied by the virtual carrier control region via a VC-PCFICH, and thenumber of symbols occupied by the host control channel region via aVC-PCFICH2. In some examples the number of symbols comprising thevirtual carrier control region 520 may be fixed, for example threesymbols. In other examples the virtual carrier control region 520 mayvary in size, for example between one and three symbols.

In some examples, the virtual carrier control region 520 may be locatedat any suitable position within the virtual carrier 530, for example inthe first few symbols of the virtual carrier 530. In the example of FIG.5, this may mean locating the virtual carrier control region 520 on thefourth, fifth and sixth symbols. However, fixing the position of thevirtual carrier control region 520 in the final symbols of the sub-framemay provide an advantage as the position of the virtual carrier controlregion 520 need not vary, even if the number of symbols of the hostcarrier control region varies. This simplifies the processing undertakenby wireless subscriber units, such as UEs, receiving data on the virtualcarrier because there is no need for them to determine the position ofthe virtual carrier control region every sub-frame as it is known thatit will always be positioned in the final symbols of the sub-frame.Furthermore, some virtual carrier control channels (e.g. the VC-PHICH,VC-PDCCH and VC-PCFICH) may occupy the first few symbols of the virtualcarrier, whereas other virtual carrier control channels, e.g. theVC-PCFICH2, may occupy the final symbols of the virtual carrier.

In some examples the virtual carrier may be located within the centrefrequency band 510 of the downlink sub-frame. In this manner, areduction in host carrier PDSCH resources caused by the insertion of oneor more virtual carriers may be minimised, since the resources occupiedby the PSS/SSS and PBCH would be contained within the virtual carrierregion and not the host carrier PDSCH region. Therefore, depending on,for example, the expected virtual carrier throughput, the location of aprimary virtual carrier can be appropriately chosen to either existinside or outside the centre band according to whether the host orprimary virtual carrier is chosen to bear the overhead of the PSS, SSSand PBCH.

Referring now to FIG. 6, a flowchart 600 of example procedures for botha low bandwidth UE to camp on to a virtual carrier and for aconventional legacy UE to camp-on to a host carrier is shown in outline.

In a conventional legacy camp-on procedure, the full or low bandwidthwireless subscriber unit, such as a full or low bandwidth UE, firstsynchronizes with the base station, such as an eNodeB, as shown in 605.The full or low bandwidth UE uses the PSS and SSS located, for example,in a generally central frequency region of the host carrier, e.g. thecentral region 510 of the host carrier of FIG. 5, as mentioned above, tosynchronize with the network, as shown in 605. In one example, the lowbandwidth UE and legacy full bandwidth UE detect the PSS and SSS in thecentre band and from these signals determine the cyclic prefix durationand the Cell ID. In LTE the PSS and SSS are only transmitted in thefirst and sixth sub-frames of each radio frame. In a different system,for example a non-LTE system, the generally central frequency region maynot be at the centre of the host carrier control region and may be wideror narrower than the 72 sub-carriers or 1.08 MHz as used in LTE.Likewise, the sub-frames may be of a different size or sizes.

The low bandwidth UE or legacy full bandwidth UE then decodes the PBCHin 610, which in one example is also carried on the generally centralfrequency region of the host carrier control region, e.g. the centralregion 510 of FIG. 5, where the PBCH includes in particular the MasterInformation Block (MIB). The MIB indicates in particular the bandwidthof the downlink carrier, the most significant bits of the System FrameNumber (SFN), and the PHICH configuration. Using the MIB carried on thePBCH, the low bandwidth UE or legacy full bandwidth UE may then be madeaware of the bandwidth of the carrier. As the full or low bandwidth UEalso knows where the generally central frequency region of the hostcarrier control region is, the full or low bandwidth UE knows the exactrange of subcarriers occupied by the downlink carrier.

For each sub-frame, the legacy full bandwidth UE then decodes thePCFICH, in 615, which is distributed across the entire bandwidth of thecarrier. As discussed above, an LTE downlink carrier can be up to 20 MHzwide (1200 sub-carriers) and an LTE full bandwidth UE therefore has tohave the capability to receive and decode transmissions on a 20 MHzbandwidth in order to decode the PCFICH. At that stage, with a 20 MHzcarrier band, the full bandwidth UE operates at a much larger bandwidththan during 605 and 610 relating to synchronization and PBCH decoding.

The legacy full bandwidth UE then establishes the PHICH locations in 620and decodes the PDCCH in 625, in particular for identifying systeminformation transmissions and for identifying its personal allocationgrants. The allocation grants are used by the legacy full bandwidth UEto locate system information and to locate the full bandwidth UE's datain the PDSCH.

At 615 to 625, the legacy full bandwidth UE decodes informationcontained in the control region, say control region 500 of FIG. 5, of asub-frame. As explained above, in LTE, the three (PCFICH, PHICH andPDCCH) control channels are located across the control region of thecarrier where the control regions extends over the system bandwidth andoccupies the first one, two or three orthogonal frequency divisionmultiplex (OFDM) symbols of each sub-frame. In a sub-frame, typicallythe (PCFICH, PHICH and PDCCH) control channels do not use all theresource elements within the control region, but they are scatteredacross the entire region, such that a legacy LTE full bandwidth UE hasto be able to simultaneously receive the entire control region 500 fordecoding each of the three (PCFICH, PHICH and PDCCH) control channels.The legacy full bandwidth UE is then able to decode the PDSCH in 630that contains system information or data transmitted for this fullbandwidth UE.

In contrast, and referring now to a low bandwidth UE operating generallyon virtual carriers, the low bandwidth UE's operation changes after 610to locate the primary virtual carrier as shown in 635. Prior to 635, thelow bandwidth UE may determine the location of the primary virtualcarrier by decoding the MIB (transmitted on the PBCH) in step 610. Thelow bandwidth UE camping on the cell to receive data on the virtualcarrier decodes the control region on the primary virtual carrier andidentifies resource blocks that have been allocated to it, in 640. Thelow bandwidth UE can then decode the PDSCH resource blocks that havebeen allocated to it or the system information, in 645. The systeminformation may occupy the same resource blocks as the host carrier ormay occupy specific resource blocks for the low bandwidth UE.

FIG. 7 illustrates PUCCH operation 700 for a low bandwidth UE, accordingto an example embodiment of the invention. In this example embodiment, aPUCCH signal is sent using a set of low frequency subcarriers 705 in afirst timeslot of a sub-frame 715. In the first timeslot of a next(second) sub-frame 720, the PUCCH signal is sent using a set of highfrequency subcarriers 725. In this manner, the PUCCH signal istransmitted across two sub-frames with a time offset (comprising thesecond timeslot of the first sub-frame) 710 between them. This timeoffset (gap) 710 of a time-multiplexed scheme allows a low frequency UEto re-tune its synthesisers and other RF circuitry before the firsttimeslot of the next (second) sub-frame 720. By inserting a switchingtime between the time at which the low bandwidth UE needs to transmit onthe set of low frequency subcarriers and the time at which it needs totransmit on the set of high frequency subcarriers, the low bandwidth UEis able to transmit PUCCH using the same physical resources as thoseused by legacy full bandwidth UEs. Since the same physical resources areused, there is no need for separate PUCCH resources 176 for the uplinkvirtual carrier: this removes the problem of the fragmentation the hostcarrier bandwidth, as illustrated in the prior art of FIG. 1.

As will be appreciated, the above approach is also compatible with thePUCCH signalling format expected by legacy UEs utilising the 3GPP™standard, in that UEs both according to this invention and legacy UEsare able to transmit in subcarriers anywhere within the entire hostcarrier bandwidth. Due to its ability to operate in a wide systembandwidth, a legacy UE does not need to re-tune its RF circuits betweentransmission of the initial low frequency subcarriers of the PUCCHsignal 705 and the subsequent high frequency subcarriers of the PUCCHsignal 725. A skilled artisan will appreciate that PUCCH can also betransmitted using high frequency subcarriers in a first timeslot and lowfrequency subcarriers in a second timeslot and that the exampleembodiment illustrated in FIG. 7 can be straightforwardly adapted toPUCCH operating in such a mode.

By introducing a blank timeslot 710, a low bandwidth UE is able totransmit frequency distributed PUCCH signals using the same physicalresources as used by PUCCH according to current 3GPP releases (up toRelease-10), without having to fragment the host carrier bandwidth,thereby providing an improvement over the prior art in FIG. 1, forexample.

FIG. 8 illustrates a low bandwidth UE operation 800, according to anexample embodiment of the invention. Initially, the UE receives anddecodes the physical downlink control channel (PDCCH) and physicaldownlink shared channel (PDSCH) in 802, 804, and determines theacknowledgement ACK or negative acknowledgement NACK status of the PDSCHin 806. The UE then determines what physical resources to use fortransmission of a physical uplink control channel (PUCCH) signal basedon the first control channel element used for PDCCH, as shown in 808.Alternatively, the UE may be semi-statically assigned some PUCCHresources to use for feedback signalling to the eNodeB, where thefeedback signalling could for example consist of ACK/NACK indications,channel quality indications (CQI), etc. The UE then performs controlchannel processing of PUCCH in order to produce a set of physicalchannel bits in 810. In this example embodiment, control channelprocessing refers to the steps required to convert the information to betransmitted on PUCCH into a bit stream. In this example embodiment,format 1a, as known in the art, is used for control channel processing,entailing multiplying a sequence of twelve complex numbers by an inputbit, wherein the input bit is a representation of an ACK/NACK status,and scrambling and spreading by a factor of ‘4’. In other examples otherformats may be used.

The UE then transmits a first half of the physical bits in a firsttimeslot of the physical resources occupied by PUCCH, say in a set oflow frequency subcarriers in 812 and then re-tunes, in 814, its radiofrequency (RF) and frequency generation circuits to a desired secondfrequency, e.g. a frequency suitable for transmitting PUCCH in a set ofhigh frequency subcarriers. The UE then waits in 816 a time period, forexample at least a timeslot, such that the time period and any re-tuningtime is, say, substantially equal to the introduced time gap asmentioned earlier. The UE then transmits a second half of the physicalbits in the first timeslot of the next sub-frame of the physicalresources occupied by the PUCCH using that set of high frequencysubcarriers, as shown in 818.

In this example embodiment, the UE only transmits an ACK/NACK on thePUCCH. However, in another example embodiment, the UE may be configuredto transmit channel quality indications (CQI), for example. In someexamples, the PUCCH may be semi-statically allocated to the UE.

FIG. 9 illustrates a schematic diagram of ‘grouped’ scheduling ofPUCCHs, according to an example embodiment of the invention. Thisillustrated example embodiment comprises a plurality of sub-frames‘1’-‘4’, wherein each sub-frame comprises PUCCH signals for UE_A 905 andPUCCH signals for UE_B 910 in anti-phase with each other. In thisexample embodiment, low frequency signals and high frequency signals forUE_A 905 and UE_B 910 are separated by at least one timeslot. Forexample, the PUCCH signal for UE_A 905 has its low frequency signal 920separated from its high frequency signal 925 by timeslot 915. Thus, eachlow frequency and high frequency signal for UE_A 905 and UE_B 910 areseparated by at least one timeslot 915.

In this example embodiment, previously blank timeslot 710 of FIG. 7,denoted 915 in this example embodiment, has been utilised by ‘grouping’a further PUCCH signal for UE_B 910 in this timeslot 915 in anti-phasewith a PUCCH signal UE_A 905. As discussed above, it is desirable tohave a time-offset, blank second timeslot 915, between the low frequencyportion of the PUCCH for UE_A 920 and the high frequency portion of thePUCCH for UE_A 925. This blank second timeslot 915 provides a lowbandwidth UE with a defined amount of time to re-tune its synthesisersand other RF circuitry during the blank second timeslot 915.

In order to make efficient use of bandwidth, it is desirable to ‘group’the PUCCH signal for UE_B 910 in the previously blank second timeslot915. As UE_B 910 is in anti-phase with UE_A 905, the PUCCH signals forlow bandwidth UE_A 905 and UE_B 910 can be easily distinguished by theeNodeB. In this example embodiment up to four different PUCCH signalscan be ‘grouped’ within the timeslots, because in the first sub-frame ofFIG. 9 the high subcarriers in the first timeslot of sub-frame 1 havenot been considered. For example, a set of subcarriers is able tosupport more than one PUCCH through code multiplexing onto thosesubcarriers (using, say, spreading and scrambling techniques). Thegrouping of UE_A 905 and UE_B 910 supports backwards compatibility andefficient resource usage when low bandwidth UEs operate in the samenetwork as high bandwidth UEs of existing or potentially futureReleases, e.g. Release 8-10 UEs.

In any one sub-frame, the resources used by the group of UEs (UE_A 905and UE_B 910) are identical to the set of resources used by a single UE,as illustrated in 140 of FIG. 1. This allows for coexistence andefficient resource usage. If two UEs are not grouped as in FIG. 9, onlythe first timeslot would be used as the upper subcarriers of the secondtimeslot could not be assigned to another UE, if that other UE was ahigh bandwidth legacy UE.

When PUCCH signals are allocated to low bandwidth UEs in a semi-staticmanner (for example for the transmission of CQI information), groups oflow bandwidth UEs are created such that the physical resources (e.g.cyclic shifts of the Zaddoff-Chu sequence) may be fully utilised in alltimeslots in both the upper and lower sets of sub-carriers.

In the example embodiment of FIG. 9, the ‘groups’ of UEs comprise pairedUEs. In other example embodiments, the ‘groups’ of UEs may comprisetime-multiplexed UEs, where ‘time-multiplexed UEs’ encompasses ascenario where there are certain UEs that are labelled as type A andother UEs as type B, but that one particular UE of type A is not alwaysallocated with one other particular UE of type B. In this exampleembodiment, each UE PUCCH signal occurs in the same relative timeslotfor each subsequent sub-frame. This is determined by the position of theother ‘paired’ UE PUCCH signal, as each ‘paired’ PUCCH signal appears inanti-phase with the other ‘paired’ PUCCH signal.

FIG. 10 illustrates a schematic of semi-statically assigned PUCCHresources for grouped UEs, according to an example embodiment of theinvention. In this illustrated example, when PUCCH is inherentlyallocated through previous allocations of PDSCH via PDCCH signalling,the relationship between PDCCH and PUCCH needs to be defined. Forexample, the grouped UEs are configured to transmit either UE_A PUCCH1005 or UE_B PUCCH 1010, as illustrated in FIG. 10. When PDSCH isallocated for one of the UEs (either UE_A or UE_B), it is automaticallyallocated for the second UE (UE_B or UE_A). The PDSCH allocation forUE_A 1005 could be defined explicitly by allocation signalling withinthe PDCCH. The PDSCH allocation for UE_B 1010 could be a known offsetfrom that for UE_A 1005. For example, UE_B 1010 may be allocated withPDSCH resource that are subcarrier multiplexed with the subcarriersapplied to the PDSCH resources for UE_A 1005 (where subcarriermultiplexing encompasses at least a use of subcarriers that are offsetin the subcarrier domain from other subcarriers. For example, the PDSCHresources for UE_B 1010 may be subcarrier multiplexed with the PDSCHresources for UE_A 1005 by assigning the subcarriers of the PDSCHresources for UE_B 1010 to be adjacent in the subcarrier domain to thesubcarriers of the PDSCH resources for UE_A 1005), or could be allocatedthe same physical resources as UE_A 1005, but in the subsequentsub-frame. The modulation and coding scheme for UE_B 1010 may beexplicitly signalled within the PDSCH.

For some MTC applications, traffic may be predictable and, therefore,automatic allocation of resources, as above, may be appropriate. Inother MTC applications, traffic may be delay tolerant, and, thus, it maybe acceptable to delay downlink transmission to one of the UEs untildownlink traffic for the other UE is also available. In some examples,automatic allocation of resources in such cases may also be appropriate.

If the network is lightly loaded, it is possible to allocate physicalresources to both UE_A 1005 and UE_B 1010 of the group, even if dataonly exists for one UE in the group, since in a lightly loaded networkthere is no penalty associated with assigning physical resources to a UEand then not using those physical resources to transfer higher layerdata.

In the example embodiment of FIG. 10, the ‘groups’ of UEs consist ofpaired UEs. In other example embodiments, the ‘groups’ of UEs maycomprise time-multiplexed UEs, where again ‘time-multiplexed UEs’encompasses a scenario where there are certain UEs that are of type Aand other UEs of type B, but that one particular UE of type A is notalways allocated with one other particular UE of type B. In this exampleembodiment, each UE PUCCH signal occurs in the same relative timeslotfor each subsequent sub-frame. The selection of the differentsubdivisions of a frequency resource (e.g. different cyclic shifts of aZadoff Chu base sequence) is determined by the position of the other‘paired’ UE PUCCH signal, as each ‘paired’ PUCCH signal appears inanti-phase with the other ‘paired’ PUCCH signal.

Although the example of FIG. 10 is described showing four cyclic shiftoptions per timeslot, it is envisaged that in other examples of theinvention more cyclic shift options per timeslot may be employed.Furthermore, in other examples of the invention, the concepts hereindescribed may be applied to more timeslots per sub-frame or frames ormultiframes.

FIG. 11 illustrates a flowchart 1100 of an eNodeB operation forscheduling ‘grouped’ UEs, according to an example embodiment of theinvention. The example flowchart 1100 assumes that PUSCH has not beenassigned to the UE (to allow the UE to transmit an ACK/NACK for thePDSCH using that PUSCH) and that the ACK/NACK indication is hencetransmitted using PUCCH. Initially, when UEs connect to the system, theeNodeB creates ‘groups’ (which in some examples may be pairs) of UEswhere one UE of the group is considered to be ‘type A’ and the other isconsidered to be ‘type B’ (depending on factors such as the amount oftime needed to switch a UE's RF circuits between two frequencies,further UEs may be considered to be ‘type C’, ‘type D’ etc.), as shownin 1102. The eNodeB then defines a relationship between PDSCH resourcesallocated, say, to ‘type B’ UEs and PDSCH resources allocated to ‘typeA’ UEs in 1104, and signals the relationship to at least the ‘type B’UEs in 1106. The eNodeB then defines a relationship between PUCCHresources for ‘type A’ and ‘type B’ UEs to the PDCCH in 1108, andsignals the relationship to at least the ‘type B’ UEs in 1110. Forexample, PUCCH resources for ‘type B’ UEs could be defined as occupyingthe timeslot after the resources for the ‘type A’ UEs and using thesubcarriers at the opposite end of the carrier to those used for ‘typeA’ UEs.

In an alternative embodiment, the relationship between PDSCH resourcesfor ‘type A’ UEs and the PDSCH resources for ‘type B’ UEs may be known apriori; furthermore the relationship between PUCCH resources for ‘typeA’ UEs and the PUCCH resources for ‘type B’ UEs may be known a priori.The eNode B, or other network node, may determine that a UE is ‘type A’or ‘type B’; alternatively UEs could be determined a priori to be of‘type A’ or ‘type B’, for example based on their International MobileEquipment Identity (IMEI) or based on subscription information stored ona subscriber identity module (SIM).

The eNodeB then waits until the next sub-frame in 1112 beforedetermining whether or not downlink data exists for at least one UE ofthe group (or pair) in 1114. If downlink data does not exist for atleast one UE of the group (or pair) in 1114, the eNodeB again waits forthe next sub-frame. However, if downlink data does exist for at leastone UE of the group (or pair) in 1114, the eNodeB allocates PDCCH, PDSCHand PUCCH resources for the group of UEs in 1116 according to theaforementioned scheduling approach. If the eNodeB determines that dataexists for ‘type A’ UEs, the eNodeB encodes that data on PDSCH for ‘typeA’ UEs in 1118. In 1120, if the eNodeB determines that data exists for‘type B’ UEs, the eNodeB encodes that data on PDSCH resources for ‘typeB’ UEs, using the relationship between ‘type A’ and ‘type B’ PDSCH thatwas defined previously. In 1122 the eNodeB then receives PUCCH for ‘typeA’ UEs on physical resources related to PDCCH according to thepreviously defined relationship. In 1124, the eNodeB then receives PUCCHfor ‘type B’ UEs on physical resources related to PDCCH according to thepreviously defined relationship. In some examples, it is noted thatthere may be some delay between 1120 and 1122 to allow the UEs to decodePDSCH and encode PUCCH.

In the example embodiment of FIG. 11, the ‘groups’ of UEs comprise ofpaired UEs. In other example embodiments, the ‘groups’ of UEs maycomprise time-multiplexed groups of more than two UEs where each UE'sPUCCH signal may occur in the same relative timeslot for each subsequentsub-frame, but located in a different set of subcarriers (such as low,medium or high frequency subcarriers). In the paired example embodiment,each UE's PUCCH signal may occur in the same relative timeslot for eachsubsequent sub-frame, but located at a different carrier frequency (suchas a low or high frequency). This low versus high carrier frequencypairing or grouping for low bandwidth UEs may be determined by theposition of the other ‘paired’ (or grouped) UE PUCCH signal, as each‘paired’ PUCCH signal appears in anti-phase with the other ‘paired’PUCCH signal.

FIG. 12 illustrates an example schematic diagram 1200 of scheduling ofPUCCHs for a first UE (UE_A) 1205, a second UE (UE_B) 1210 and a thirdUE (UE_C) 1215, according to an example embodiment of the invention. Inthe time-multiplexed mode of operation shown in the example schematicdiagram 1200, the PUCCH resources that the UEs are assigned to mayappear similar to the PUCCH resources (e.g. sub-frame or timeslot)assigned in the ‘grouping’ mode of operation illustrated in FIG. 9.However, the scheduler (not shown) has a greater degree of freedom inthis example with regard to which UEs to schedule to a particular PUCCHresource. Thus, in this example embodiment and in contrast to thescheduling of FIG. 11 relating to ‘pairing’ of PUCCH signals, thescheduler does not automatically schedule a paired UE when the other UEof the pair is scheduled. Thus, in this example embodiment, UE_A hasbeen paired with UE_B in sub-frame 1 and sub-frame 2, but in sub-frame 3and sub-frame 4 UE_A has been paired with UE_C, rather than with UE_B.

For example, in sub-frames one and two, UE_A 1205 is time-multiplexedwith UE_B 1210 between respective first timeslots 1220, 1230 and secondtimeslots 1225, 1235 of the respective sub-frames. However, insub-frames three and four, UE_A 1205 is time-multiplexed with UE_C 1215between respective first timeslots 1240, 1250 and second timeslots 1245,1255 of the respective sub-frames. Therefore, in this exampleembodiment, it is possible to alter the pairing of PUCCHs betweendifferent sub-frames.

In an example embodiment, the actual PUCCH that the UE uses can besemi-statically configured by radio resource control signalling.

In a further example embodiment, the PUCCH that the UE uses may bearranged to be a function of the index of the first control channelelement (CCE) used to transmit the PDCCH that allocates some PDSCHresource. This example may be employed where the PUCCH is required toreport acknowledgement/negative acknowledgement (ACK/NACK) informationon a PDSCH that was previously allocated to the UE.

In a further example embodiment, where the PUCCH is a function of thefirst control channel element (CCE) used to transmit the PDCCH, a newmapping between PDCCH and PUCCH may be defined. This new mapping can beapplied only to the low bandwidth UEs to which this invention applies.

In this example embodiment, as per Release-10 LTE, the PUCCH that the UEshall use is defined by the first CCE that is occupied by the PDCCH.PDCCHs with some first CCEs are associated with ‘type A’ PUCCH andothers are associated with a ‘type B’ PUCCH. The UE transmits a ‘type A’PUCCH or a ‘type B’ PUCCH depending on the first CCE used for the PDCCH.Low bandwidth UEs are allocated PDCCH with consideration for the PUCCHresources (type ‘A’ or ‘type B’) that they shall use. Legacy UEs can beallocated using the legacy mapping rules between PDCCH and PUCCH as perRelease-10. The scheduler (not shown) manages the assignment of PUCCH asa function of UE type and of the first CCEs used for the PDCCH.

FIG. 13 illustrates a schematic diagram 1300 of the scheduling of PDCCH1305 and PDSCH 1310 on a downlink carrier 1330 and the scheduling ofdifferent example types of PUCCHs on a corresponding uplink carrier 1335according to an example embodiment of the invention. In one example, itis assumed that a PDCCH 1305 whose first CCE 1315 occupies a firstresource ‘X’ 1360 maps to a specific type of PUCCH, for example ‘type A’PUCCH 1320, and that a PDCCH 1305 whose first CCE occupies a secondresource ‘Y’ 1350 maps to a specific type of PUCCH, for example ‘type B’PUCCH 1325. This figure also shows that PDCCH 1305 allocates PDSCH 1310resources (noting that the PUCCH 1320, 1325 may carry the ACK/NACK forthe PDSCH 1310).

FIG. 14 illustrates a flowchart 1400 of an eNodeB scheduling of PDSCH toUEs, according to an example embodiment of the invention. This exampleembodiment relates to the case where PUCCHs are time-multiplexed, andapplies to both low bandwidth UEs and to legacy UEs. In this example, itis assumed that when PDCCH allocates PDSCH (there is an implication thatthere then follows a PUCCH), there is a one-to-one mapping between thefirst control channel element used for the PDCCH (that allocates PDSCH)and the PUCCH that is associated with the PDSCH. Hence, in this example,selecting a PUCCH to be used is inherently linked with selecting aPDCCH.

Initially, the eNodeB creates a list of PUCCH physical resources alreadyallocated for use in future sub-frames in 1402, and initiates asub-frame index in 1404. The eNodeB then determines in 1406 as towhether the UE to be scheduled is a low bandwidth UE or a legacy UE. Ifthe eNodeB determines that the UE to be scheduled is a low bandwidth UE,the eNodeB uses a low bandwidth UE PDCCH to PUCCH mapping rule, as shownin 1410. If the eNodeB determines that the UE to be scheduled is alegacy UE, the eNodeB uses a legacy PDCCH to PUCCH mapping rule, asshown in 1408.

The eNodeB then schedules the UE using a PDCCH, such that the UE willuse PUCCH physical resources that have not been previously allocated in1412. This process is required when PDCCH allocates PDSCH with theimplication that there then follows a PUCCH. This is because inRelease-10, there is a one-to-one mapping between the first controlchannel element used for the PDCCH, which allocates PDSCH, and the PUCCHthat is associated with the PDSCH. Therefore, choosing a PUCCH to beused is linked with choosing a PDCCH. Furthermore, use of a certainPDCCH in a sub-frame ‘n’ may not be possible when a certain other PDCCHwas used in a sub-frame ‘n−1’ and the PUCCHs associated with thosePDCCHs may clash in a future sub-frame in the uplink.

The eNodeB then updates a list with those PUCCH physical resources thathave been assigned on the current sub-frame, as shown in 1414. TheeNodeB then determines whether more UEs can be allocated in the currentsub-frame in 1416. In one example, this decision depends upon whetherPDCCH, PUCCH and PDSCH are available. However, assuming there is theavailability of PDCCH, PUCCH and PDSCH, the eNodeB considers the next UEin the schedule in 1418, if it determines that more UEs can be allocatedin the sub-frame. Otherwise, the eNodeB increments the sub-frame indexin 1420. Following either 1418 or 1420, the eNodeB returns to 1406 todetermine whether the next UE in the schedule is a low bandwidth UE. Itis noted in this example, that the use of a certain PDCCH in sub-frame‘n’ may not be possible when a certain other PDCCH was used in sub-frame‘n−1’ and the PUCCHs associated with those PDCCHs may clash in a futuresub-frame (in the UL).

In one example, it is possible that PUCCH resources can besemi-statically assigned to UEs for the purposes of periodic CQIreporting. In such a semi-static case, the PUCCHs to be used bydifferent UEs, for example a mix of low bandwidth and legacy UEs, may bedecided when UEs connect to the system and those PUCCH resources wouldnot change with time, unless the UE is re-configured using well knownre-configuration procedures.

Although examples have been described showing sub-frames with twotimeslots, it is envisaged that in other examples of the invention moretimeslots per sub-frame may be employed, so long as sufficient switchingand re-tuning time is provided for the low bandwidth wirelesscommunication units. Furthermore, in other examples of the invention,the concepts herein described may be applied to frames or multiframes.

Although examples have been described showing a time offset 710 of asingle timeslot, it is envisaged that in other examples, more than onetimeslot or fractions of a timeslot may be employed as a time offset.

Thus, in some example embodiments, low bandwidth wireless communicationunits (e.g. UEs) may now be able to operate within a high bandwidthcarrier without fragmenting the contiguous uplink resource available inthe high bandwidth carrier. Furthermore, in some example embodiments,with a provision of a time gap between the UE having to transmit on somesubcarriers and then having to transmit on another set of subcarriers,the use of UEs with a restricted bandwidth within a higher bandwidthcarrier may be supported. In addition, in some example embodiments, UEsmay be paired such that they operate in anti-phase. In some exampleembodiments, UEs may not be paired and may be scheduled to use differentPUCCH resources (for example according to the aforementioned‘time-multiplexed’ scheme). In some example embodiments, when UEs arepaired, and the application is delay tolerant, the pair of UEs may bescheduled either when downlink traffic exists for both UEs (which mayentail buffering of traffic for the earlier UE until data appears forthe later UE); or when there is spare resource within the sub-frame dueto, for example, a lull in the amount of traffic being offered to thesystem.

It will be appreciated that, for clarity purposes, the above descriptionhas described embodiments of the invention with reference to differentfunctional units and processors. However, it will be apparent that anysuitable distribution of functionality between different functionalunits or processors can be applied, without detracting from theinvention. For example, functionality illustrated to be performed byseparate processors or controllers may be performed by the sameprocessor or controller. Hence, references to specific functional unitsare only to be seen as references to suitable means for providing thedescribed functionality, rather than indicative of a strict logical orphysical structure or organization.

Aspects of the invention may be implemented in any suitable formincluding hardware, software, firmware or any combination of these. Theinvention may optionally be implemented, at least partly, as computersoftware running on one or more data processors and/or digital signalprocessors. Thus, the elements and components of an embodiment of theinvention may be physically, functionally and logically implemented inany suitable way. Indeed, the functionality may be implemented in asingle unit, in a plurality of units or as part of other functionalunits.

Those skilled in the art will recognize that the functional blocksand/or logic elements herein described may be implemented in anintegrated circuit for incorporation into one or more of thecommunication units. Furthermore, it is intended that boundaries betweenlogic blocks are merely illustrative and that alternative embodimentsmay merge logic blocks or circuit elements or impose an alternatecomposition of functionality upon various logic blocks or circuitelements. It is further intended that the architectures depicted hereinare merely exemplary, and that in fact many other architectures can beimplemented that achieve the same functionality. For example, forclarity the control processor 296 and signal processor 308 have beenillustrated and described as a single processing module, whereas inother implementations it may comprise separate processing modules orlogic blocks.

Although the present invention has been described in connection withsome example embodiments, it is not intended to be limited to thespecific form set forth herein. Rather, the scope of the presentinvention is limited only by the accompanying claims. Additionally,although a feature may appear to be described in connection withparticular embodiments, one skilled in the art would recognize thatvarious features of the described embodiments may be combined inaccordance with the invention. In the claims, the term ‘comprising’ doesnot exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means,elements or method steps may be implemented by, for example, a singleunit or processor. Additionally, although individual features may beincluded in different claims, these may possibly be advantageouslycombined, and the inclusion in different claims does not imply that acombination of features is not feasible and/or advantageous. Also, theinclusion of a feature in one category of claims does not imply alimitation to this category, but rather indicates that the feature isequally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply anyspecific order in which the features must be performed and in particularthe order of individual steps in a method claim does not imply that thesteps must be performed in this order. Rather, the steps may beperformed in any suitable order. In addition, singular references do notexclude a plurality. Thus, references to ‘a’, ‘an’, ‘first’, ‘second’,etc. do not preclude a plurality.

1. A method for transmitting on at least one resource, the methodcomprising, at a wireless communication unit: receiving and decoding adownlink signal from a network element wherein the signal allocates atleast one uplink physical resource comprising a first portion of a firstsub-frame on a first frequency and a first portion of a second sub-frameon a second frequency wherein a time gap is allocated between an end ofthe first portion of the first sub-frame and a beginning of the firstportion of a second sub-frame; transmitting a first half of physicalbits in a first timeslot of the determined at least one uplink physicalresource; re-tuning the wireless communication unit's radio frequency,RF, generation circuit to the second frequency; and waiting a timeperiod before transmitting a second half of the physical bits in a firsttimeslot of the second sub-frame of the determined at least one uplinkphysical resource.
 2. The method of claim 1 further comprising:determining at least one uplink physical resource to use for atransmission to the network element based on the decoded signal; andperforming control channel processing of the determined at least oneuplink physical resource in order to produce a set of physical channelbits for transmission.
 3. The method of claim 1 further comprisingdetermining at least one uplink physical resource to use for feedbacksignalling to the network element, wherein the feedback signallingcomprises an acknowledgement, ACK, or negative acknowledgement, NACK,status of the decoded signal, or a channel quality indication, CQI,signal.
 4. The method of claim 1 wherein the decoded signal is receivedin a physical downlink control channel, PDCCH, and physical downlinkshared channel, PDSCH, allocation.
 5. The method of claim 1 wherein thedecoded signal comprises a first control channel element used for PDCCH.6. A wireless communication unit comprising: a receiver for receiving adownlink signal from a network element (802, 804); a signal processorfor decoding the downlink signal wherein the signal allocates at leastone uplink physical resource comprising a first portion of a firstsub-frame on a first frequency and a first portion of a second sub-frameon a second frequency wherein a time gap is allocated between an end ofthe first portion of the first sub-frame and a beginning of the firstportion of a second sub-frame; and a transmitter for transmitting afirst half of physical bits in a first timeslot of the determined atleast one uplink physical resource; wherein the signal processor isarranged to re-tune the wireless communication unit's radio frequency(RF) generation circuit to the second frequency; and the transmitter isarranged to transmit (816) a second half of the physical bits in a firsttimeslot of the second sub-frame of the determined at least one uplinkphysical resource.
 7. The wireless communication unit of claim 6 whereinthe signal processor is arranged to wait a time period before initiationof a transmission of a second half of the physical bits in a firsttimeslot of the second sub-frame of the determined at least one uplinkphysical resource.
 8. The wireless communication unit of claim 6 whereinthe signal processor is arranged to determine (808) at least one uplinkphysical resource to use for a transmission to the network element basedon the decoded downlink signal.
 9. The wireless communication unit ofclaim 8 wherein the signal processor is arranged to perform controlchannel processing of the determined at least one uplink physicalresource in order to produce a set of physical channel bits fortransmission.
 10. The wireless communication unit of claim 1 wherein thesignal processor is arranged to determine at least one uplink physicalresource to use for feedback signalling to the network element.
 11. Thewireless communication unit of claim 1 wherein feedback signallingcomprises an acknowledgement, ACK, or negative acknowledgement, NACK,status of the decoded downlink signal, or a channel quality indication,CQI, signal.
 12. The wireless communication unit of claim 1 wherein thedecoded signal is received in a physical downlink control channel,PDCCH, and physical downlink shared channel, PDSCH, allocation.
 13. Thewireless communication unit of claim 1 wherein the decoded signalcomprises a first control channel element used for PDCCH.
 14. Anintegrated circuit for a wireless communication unit comprising a signalprocessor arranged to: decode a downlink signal from a network elementwherein the signal allocates at least one uplink physical resourcecomprising a first portion of a first sub-frame on a first frequency anda first portion of a second sub-frame on a second frequency wherein atime gap is allocated between an end of the first portion of the firstsub-frame and a beginning of the first portion of a second sub-frame;and re-tune the wireless communication unit's radio frequency, RF,generation circuit to the second frequency; and the transmit a secondhalf of the physical bits in a first timeslot of the second sub-frame ofthe determined at least one uplink physical resource.